Why Have Two Desktop Operating Systems?

Microsoft Corporation

Created: July 1994

Introduction

It is important to understand that there are two distinct design points for Microsoft's family of operating systems—one centered on the mainstream system (in 1994), and another centered on the leading-edge system. It is not currently possible to have one operating system implementation that fully exploits the broad range of hardware available at any point in time. For mainstream systems (currently represented by products such as sub-notebook and entry-level desktop machines), the Microsoft® Windows® 95 design goal is to deliver responsive performance for a broad range of applications while conserving the amount of system resources used. On the leading-edge system (for example, a dual-processor workstation or multi-processor RISC server), Windows NT™ was designed to fully exploit the capabilities of the hardware and provide the most advanced services for the most demanding applications.

As a result of the requirements placed on the new enterprise solutions, all major operating system developers have recognized the necessity of moving to a micro-kernel architecture for their leading-edge operating systems. This includes Microsoft, IBM, Sun (and most UNIX® vendors), and Novell. Only Microsoft made this commitment over 5 years ago and began shipping Windows NT to developers in July 1992 with general availability in July 1993. This architecture allows vendors to enhance systems to respond to the rapidly changing requirements of the business solutions being developed, while maintaining flexibility to exploit new hardware and peripherals.

Both Windows 95 and Windows NT Workstation provide a common base of functionality that is required by all customers, including ease of use, power, connectivity, and manageability. Microsoft is committed to, and will deliver, parity in basic functionality (such as the user interface) to each platform as quickly as possible. The further differences between the two platforms are a result of their different design goals. Windows 95 is focused on making computing easier for anyone using a wide range of personal and business applications on desktop and portable computers. To protect their current investment, these users require the highest level of compatibility with today's applications and device drivers.

Windows NT Workstation is focused on providing the most powerful desktop operating system for solving complex business needs. For developers; technical, engineering, and financial users; and business operations application users, it delivers the highest level of performance to support the most demanding business applications. It also provides the highest levels of reliability, protection, and security for those applications that you can't afford to have fail while exploiting the latest hardware innovations such as RISC processors and multi-processor configurations. This focus on solving business needs is also reflected in the emphasis on maintenance and regular system updates.

Over time, as mainstream machines become more powerful, technologies implemented first on the leading-edge Windows operating system product will migrate to the mainstream product. Sometimes technical innovations will appear first on the mainstream product, due to timing of releases or because some features are focused on ease of use for general end-users. The guiding principle for product planning is for the leading-edge product to provide a superset of the functionality in the mainstream product.

For application developers, Microsoft has only one Windows programming platform, defined by Win32® (the 32-bit Windows application programming interface) and OLE. By following a few simple guidelines, developers can write a single application that runs across the Windows operating system product family. If they wish, developers can target specific operating system products because the functionality they provide is important to their particular application, but that is not a requirement.

Usage Scenarios

The decision about which platform to deploy should be based on what tasks people are trying to accomplish. The two platforms provide a very complementary set of capabilities that can accommodate a broad range of use scenarios. Consider the following examples:

• Most office environments require people to perform a variety of general tasks such as word processing, database queries, or spreadsheet analysis, using productivity applications such as the Microsoft Office suite. They may also be using applications that are specific to their particular business. Most companies have an installed base of personal computers, peripheral devices, and applications, and want to maximize their investment in that computing infrastructure. For them, Windows 95 is the best choice.
  
  
• Many companies have employees who spend a high fraction of their working hours away from their office, whether they're at a customer site, in a hotel, or out in the field, and rely on personal computers to help them perform their jobs. These mobile computer users have similar requirements for application and device compatibility, but also need an operating system that places lower demands on the hardware, including amount of memory, battery power, and use of disk space. For these customers, Windows 95 is also the best choice.
  
  
• Engineers, scientific researchers, statisticians, and other technical users often need the capability to use processing-intensive applications for data analysis and large design activities. Windows NT Workstation, with its support for symmetric multiprocessing (SMP) and its portability to different high-performance platforms such as those based on Pentium™, DEC® Alpha™, or MIPS® CPUs, can provide the performance of a leading-edge workstation or minicomputer at a fraction of the cost. Moreover, Windows NT Workstation still runs personal productivity applications on the same machine.
  
  
• In industries that need to protect sensitive data or application files, such as banking and defense, Windows NT Workstation is the right choice for the secure desktop. The NTFS file system, combined with appropriate security procedures, helps prevent unauthorized access to systems and data. Moreover, the security model in Windows NT Workstation is designed to be compliant with C2-level certification. With these features, a Windows NT system can even be shared by multiple users and still maintain security for all files on the system.
  
  
• Many users require very high levels of availability and performance, and cannot afford down time, regardless of the application they are running. Very often, these types of systems are being "right-sized" from mini and mainframe systems. For example, many manufacturing systems today use 16-bit applications to manage their company's production line. Windows NT Workstation supports running these Win16 applications in separate address spaces (often referred to as separate virtual machines). For users, this means that even if one of these applications fails, all of the other applications continue to run. Windows NT Workstation also provides complete protection for 32-bit applications and the ability to automatically recover (reboot of necessary) if the system goes down.

Similarities

Differences